That should repair if you roughen up the inside glue it in place then get some resin and woven glass mat and glue it inside the corner ensure the patch is big enough to cover a nice area past the break. Couple of rivets for peace of mind and that should be strong enough. Even put a metal plate in if you like.
£20.00 job done.
Hi Frosti,
Remember you can buy the REAR part of the case new from BMW (£78) and swop over the lid and locking handle mechanism - not a difficuly job.
All parts for the system cases are available individually
If it was the bottom edge of the pannier i would say patch it but as the lug has broken off and it takes a good portion of the weight of the loaded pannier i would go for a new or secondhand half pannier
Couple on E Bay at the moment with 99p staring prices and no bids with only a couple of days left